If we find "alien" life on other planets, it will be most likely only sentient life...no humans or advanced civilizations as we love to fantasize about. UFO activity, crop circles, abductions, etc are all from inter-dimensional beings, not extra-terrestrial. I highly suspect that they're demons masquerading as our "space brothers", given the fact that everything is done so secretively (i.e. occult). So if someone were to take this question seriously, I would say that it answers itself without any further need for discussion.